Method and system for providing inbound traffic redirection solution

ABSTRACT

The present invention provides a method for redirecting roaming traffic of a roamer associated with an HPMN and currently roaming in a first VPMN. The method includes detecting by a detection unit coupled to the first VPMN, a registration attempt of the roamer at a second VPMN, upon receipt of a first registration cancellation message of one or more registration cancellation messages, sent by the HPMN. Finally, the method includes causing the HPMN to send a registration response message to a VLR associated with the second VPMN, to thwart the registration attempt of the roamer at the second VPMN, by sending one or more registration messages to the HPMN from a redirection unit coupled to the first VPMN. The redirection unit further facilitates the roamer&#39;s mobile communication when the roamer&#39;s handset gets stuck in the second VPMN.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/815,840 entitled “A network-based framework forretaining inbound roamers—Inbound-Traffic Redirection Based on HLRerrors or VLR errors,” filed on Jun. 23, 2006. This application alsoclaims the benefit of U.S. Provisional Patent Application Ser. No.60/818,283 entitled “A network-based framework for retaining inboundroamers—Inbound-Traffic Redirection Based on HLR errors or VLR errors,”filed on Jul. 5, 2006. This application also claims the benefit of U.S.Provisional Patent Application Ser. No. 60/872,769 entitled “Anetwork-based framework for retaining inbound roamers—Inbound-TrafficRedirection Based on HLR errors or VLR errors and integration withgateway location register and mechanisms for handling stuck handset,”filed on Dec. 5, 2006. Further, this application is acontinuation-in-part of U.S. patent application Ser. No. 11/402,128entitled “Method and Apparatus for Redirection of Inbound RoamerTraffic,” filed on Apr. 12, 2006, and a continuation-in-part of U.S.patent application Ser. No. 11/374,437 entitled “Method and Apparatusfor Defense Against Network Traffic Redirection,” filed on Mar. 14,2006, now U.S. Pat. No. 7,684,793 claiming priority to Mar. 14, 2005,and a continuation-in-part of U.S. patent application Ser. No.10/635,804 entitled “Method And System For Cellular Network TrafficRedirection,” now U.S. Pat. No. 7,072,651, filed on Aug. 5, 2003,claiming priority to Aug. 5, 2002. All of these related patentapplications are incorporated herein by this reference in theirentireties.

FIELD OF THE INVENTION

The present invention generally relates to roamers in mobile networks.More specifically, the invention relates to controlling traffic of theseroamers.

BACKGROUND OF THE INVENTION

Many companies and network operators deploy common carrier mobilecommunication systems in almost every country around the world. Many ofthose network operators offer international roaming to their subscriberstraveling abroad, and to travelers visiting their territory who usetheir foreign mobile phones. Such an offering enables public mobilenetwork (PMN) subscribers to use their mobile phones within the PMNsother than their own, such as the networks present in territories otherthan those covered by the network to which they normally subscribe.

Typically the network operators enter preferred bilateral roamingagreements (“partnerships”) with each other that include more favorableroaming charges than those offered operators with whom they haveestablished no such partnerships. Therefore, “preferred” visitednetworks are those that the home network prefers its outbound roamers toregister with, when traveling outside their home coverage area, normallyby virtue of such a partnership. Non-partner networks are“non-preferred” networks. Hence, the network operators can maximizetheir margins and the roamers can get more attractive roaming rates andbetter services if roamers roam on their home mobile operator'spreferred (or partner) networks.

Subscribers may roam in one or more visited network(s) (i.e. VisitedPublic Mobile Networks (VPMN)) that may or may not be in the samecountry as their home network (i.e. Home Public Mobile Networks (HPMN)).In some cases a “non-preferred” VPMN may manage to get the subscribersfrom the HPMN, primarily due to “preferred” VPMN's failure in radiocoverage, or manual selection by the subscriber of HPMN. This may alsobe due to traffic distribution by the HPMN Traffic Redirection (TR) (orSteering of Roaming (SoR)). Sometimes the HPMN operators use TRtechniques to control the traffic distribution of the roamers amongVPMNs in a country so that the “preferred” VPMN gets a higher percentageof the HPMN's roaming traffic as compared to the “non-preferred” VPMNs.However, these TR techniques may deprive the non-preferred VPMNoperators of inbound roaming revenues. In some cases, these deprivedVPMN operators may even have a partnership with the HPMN and be one ofthe “preferred” networks. In addition, TR technique, which typicallyfunctions by rejecting registration attempts, timing out or aborting thehandset's attempt to register on a new VPMN, can generate network errorson the subscriber's mobile handset's radio interface. This compels themobile handset to re-initiate a number of registration attempts, whichunnecessarily overloads the network interface between the HPMN and theVPMN.

In some cases, competing and “non-preferred” VPMN operators may deploy aform of TR at their end to retain the inbound roamers (i.e. subscribersof HPMN) by stopping them from leaking out of their network. Thisdecreases the revenues for other VPMN operators. The TR that these VPMNoperators deploy is actually an inbound TR (ITR) solution to retain theinbound roaming subscribers.

The prior art also provides Anti-TR techniques designed to improve thechances of an inbound roamer registering successfully at a VPMN evenwhen an HPMN is applying the TR against the VPMN. Other prior arttechniques provide an anti-ITR system to counter a competitor VPMN's ITRattempt. One or more earlier filings provided integrated solutions toachieve the desired traffic redirection. In one case, the ITR andanti-TR solutions were integrated to handle the situation where an HPMNHLR issues a rejection error message to a VPMN in a location updateresponse message. In another case, the ITR and anti-ITR solutions wereintegrated to help a VPMN operator retain the inbound roamer fromleaking to other VPMNs. In one or more of the above solutions, arejection error message that the HPMN HLR sends to the competitor VPMN,helps the VPMN operator to retain its inbound roamer. This rejectionerror message causes a failure of the inbound roamer's registrationprocess with the competitor VPMN, and is usually termed as HPMN HLRabort.

However, the prior art TR, ITR anti-TR and anti-ITR techniques did notcover the scenario where a competitor VPMN VLR, instead of the HPMN HLR,aborts the registration attempt of the inbound roamer at the competitorVPMN. As the competitor VPMN VLR aborts the registration attempt, it isreferred to as competitor VLR abort. Moreover, one or more of the abovementioned solutions did not consider the case when the inbound roamer'shandset got stuck either during his registration attempt at thecompetitor VPMN or after his successful registration with the competitorVPMN.

In accordance with the foregoing, there is a need in the art for asystem and method which allow a VPMN operator to perform trafficredirection on the inbound roamers, in order to cause the VLR of thecompetitor VPMN to abort the inbound roamer's registration attempt atthe competitor VPMN. This helps the VPMN operators to retain its inboundroamers. There is also a requirement to alleviate the problem of stuckhandset, as described above.

SUMMARY

The present invention is directed to provide a method for redirectingroaming traffic of a roamer, associated with an HPMN, and currentlyroaming in a first VPMN, where the roamer may attempt to register withanother network that is located in the same country or different countryas first VPMN. The method includes detecting by a detection unit, aregistration attempt of the roamer at a second VPMN, upon receipt of afirst registration cancellation message of one or more registrationcancellation messages at the first VPMN, sent by the HPMN. The methodfurther includes causing the HPMN to send a registration responsemessage to a VLR associated with the second VPMN, to thwart theregistration attempt of the roamer at the second VPMN, by sending one ormore registration messages to the HPMN from a redirection unit. Theredirection unit and the detection unit are coupled to the first VPMN.The redirection unit further facilitates the roamer's mobilecommunication when the roamer's handset gets stuck in the second VPMN.

Another aspect of the invention presents a system for redirectingroaming traffic of a roamer, associated with an HPMN, and is currentlyroaming in a first VPMN, where the roamer may attempt to register withanother network that is located in the same country or different countryas first VPMN. The system includes a detection unit coupled to the firstVPMN that detects a registration attempt of the roamer at a second VPMN,upon receipt of a first registration cancellation message of one or moreregistration cancellation messages at the first VPMN from the HPMN. Thesystem further includes a redirection unit coupled to the first VPMN forsending one or more registration messages to the HPMN to cause the HPMNto send a registration response message to a VLR associated with thesecond VPMN that thwarts the registration attempt of the roamer at thesecond VPMN. Thereafter, the redirection unit facilitates the roamer'smobile communication when the roamer's handset gets stuck in the secondVPMN.

BRIEF DESCRIPTION OF DRAWINGS

In the drawings, the same or similar reference numbers identify similarelements or acts.

FIG. 1 represents a system for implementing Inbound Traffic RedirectionSystem (ITRS) solution, in accordance with an embodiment of the presentinvention;

FIG. 2 is a flowchart for implementing ITRS solution in a VisitorLocation Register (VLR) error based approach, in accordance with anembodiment of the present invention;

FIG. 3 represents a flow diagram for providing enhanced location basedITR to cause a competitor VLR abort in the VLR error based approach, inaccordance with an embodiment of the present invention;

FIG. 4 represents a flow diagram for providing location recovery basedITR in the VLR error based approach, in accordance with an embodiment ofthe present invention;

FIG. 5 represents a flow diagram for performing ITR in conjunction withcountering of TR attempt initiated by the HPMN in the VLR error basedapproach, in accordance with an embodiment of the present invention;

FIG. 6 represents a flow diagram for performing the ITR to counter anITR attempt from a competitor network, in accordance with an embodimentof the present invention;

FIGS. 7A, 7B, and 7C represent a flow diagram for handling a stuckhandset case, when the roamer's handset is stuck during its registrationattempt at the competitor network, in accordance with a first embodimentof the present invention;

FIGS. 8A, 8B, and 8C represent a flow diagram for handling a stuckhandset case, when the roamer's handset is stuck after it issuccessfully registered at the competitor network, in accordance with asecond embodiment of the present invention.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, specificnumbers, materials and configurations are set forth in order to providea thorough understanding of the invention. It will be apparent, however,to one having ordinary skill in the art, that the invention may bepracticed without these specific details. In some instances, well-knownfeatures may be omitted or simplified, so as not to obscure the presentinvention. Furthermore, reference in the specification to “oneembodiment” or “an embodiment” means that a particular feature,structure or characteristic, described in connection with theembodiment, is included in at least one embodiment of the invention. Theappearance of the phrase “in an embodiment”, in various places in thespecification, does not necessarily refer to the same embodiment.

The present invention provides a system, a method, and a computerprogram product, to control traffic of a roamer, associated with a homenetwork, between a first visited network, a competitor's visited networkand the home network. The system provides an Inbound Traffic Redirection(ITR) architecture that allows that first visited network operator toretain its inbound roamers. The system further provides a VLR errorbased approach, for use when a Visitor Location Register (VLR)associated with the competitor visited network itself aborts theregistration attempt of the roamer at the competitor visited network.This allows the operator of that first visited network to retain itsinbound roamers.

The system allows a visited network operator to authenticate the inboundroamer with his home network in case the home network has suchauthentication requirement. The system also allows the visited networkoperator to blacklist and whitelist either a Home Location Register(HLR) associated with the home network, or Visited Mobile SwitchingCenter/Visited Location Register (VMSC/VLR) associated with thecompetitor visited network, or a combination of both. This blacklistingand whitelisting is performed based on various criteria, which aredescribed later in context of the present invention. The system alsohandles various cases when the inbound roamer's handset gets stuck dueto the ITR attempt by the visited network. This may either happen duringthe inbound roamer's registration attempt at the competitor visitednetwork, or after his successful registration with the competitorvisited network. The system also provides a Gateway Location Register(GLR) based solution that allows the visited network to create asynthetic (referred to here as “fake”) traffic distribution image at theHPMN HLR that eventually results in maximizing roaming revenues of thevisited network operator, since the HLR diverts the roaming traffic tothe visited network. Various embodiments of this GLR based fakingsolution are described later in context of the present invention.

Earlier approaches (“previous ITR”), such as that taught by the inventorof U.S. patent application Ser. No. 11/402,128, filed on Apr. 12, 2006,provide ways of allowing a network operator to deploy a network-side MAPsignaling-based solution to retain inbound roamers on its network. Inother words, those approaches provide techniques for performing ITR.FIG. 1 represents a system 100 for providing an Inbound TrafficRedirection System (ITRS) solution. This ITRS solution allows trafficredirection of the roamers, associated with a Home Public Mobile Network(HPMN) 102, in a first Visited Public Mobile Network (VPMN) 104. Aroamer 106, who is originally a subscriber of HPMN 102, registers withfirst VPMN 104 (represented in dashed line in FIG. 1). In some cases,roamer 106 may attempt to (or is forced to) register with a second VPMN108 (i.e. competitor visited network). HPMN 102 includes a Home LocationRegister (HLR) 110, which is hereinafter referred to as HLR-H 110. Itwill be apparent to a person skilled in the art that HLR-H 110 storesprofile data corresponding to all roamers of HPMN 102.

Techniques by which an HPMN can steer outbound roamers to preferredVPMNs are known, and referred to here as “previous TR.” In oneembodiment of the present invention, HPMN 102 may include a TR module(not shown in FIG. 1) that is used to redirect the roaming traffic ofits outbound roamers to a “preferred” visited network. For example, ifsecond VPMN 108 is a preferred network of HPMN 102, HPMN 102 willattempt to redirect the traffic of roamer 106 to second VPMN 108, usingthe TR module deployed at its network.

Techniques by which a VPMN operator can counter attempts by an HPMN atoutbound traffic redirection are also known. For instance, examples ofsuch “previous anti-TR” are taught by the inventor of U.S. patentapplication No. 60/662,030 filed on Mar. 14, 2005, System 100 mayoptionally include in first VPMN 104, an anti-TR module (not shown inFIG. 1) for countering the HPMN's TR attempt. Various embodiments wherethe VPMN operator counters the HPMN TR attempts, in addition to the ITRSsolution are described later in conjunction with FIG. 5.

System 100 includes in first VPMN 104, a first VPMN VLR 112 that isintegrated with a VMSC in first VPMN 104. Similarly, second VPMN 108includes a second VPMN VLR 114 that is integrated with a VMSC in secondVPMN 108. As first VPMN VLR 112 and its integrated VMSC reside in firstVPMN 104, they are interchangeably referred to as VMSC/VLR-V1 112.Similarly, second VPMN VLR 114 and its integrated VMSC areinterchangeably referred to as VMSC/VLR-V2 114. Notwithstanding, boththe VPMN VLRs and the VMSCs may have different logical addresses. Roamer106's signaling in first VPMN 104 is routed via a switch/roaming STP-V1116 and an international STP1 118 to HPMN 102. Similarly, roamer 106'ssignaling in second VPMN 108 is routed via a switch/roaming STP-V2 120and an international STP2 122 to HPMN 102. HPMN 102 communicates withfirst VPMN 104 and second VPMN 108 using Signaling System #7 (SS7)signaling architecture 124 involving an international STP3 126 connectedto a switching/roaming STP-H 128 in HPMN 102. The signals exchangedbetween different networks are Transaction Capabilities Application Part(TCAP) including Mobile Application Part (MAP), Camel Application Part(CAP) and the like based signals. In another embodiment of the presentinvention, the signals exchanged are Signaling Connection Control Part(SCCP) based routing signals.

Roamer 106 may attempt to register with second VPMN 108, even though heis already registered with first VPMN 104, due to one or more of thefollowing reasons. For example, roamer 106 may attempt to change theVPMN network in case there is weak signal strength or a loss of coveragein first VPMN 104, or due to new available technology (e.g., GPRS or 3G)in second VPMN 108. In another case, HPMN 102 may redirect the trafficof roamer 106 to some other network operator in second VPMN 108, eventhough an operator in HPMN 102 may have a roaming relationship withfirst VPMN 104. In yet another embodiment of the invention, this networkreselection may also be due to preferred PLMN timer on roamer 106'shandset, indicating preference of second VPMN 108 over first VPMN 104.This steering of traffic deprives the operator in first VPMN 104 of therevenue from roamer 106.

System 100 further includes in first VPMN 104, an ITR module 130 thatmonitors the traffic between HPMN 102 and first VPMN 104, and issues oneor more signaling messages in order to attempt to redirect roamer 106'straffic to first VPMN 104. In one embodiment of the invention, theoperator in first VPMN 104 deploys ITR module 130 to counter the TRattempt by the operator in HPMN 102, and the ITR attempt by the operatorin second VPMN 108. ITR module 130 includes a detection unit 132 formonitoring the MAP signaling messages exchanged between STP-V1 116, andinternational STP1 118. This monitoring is referred to as passivemonitoring. ITR module 130 further includes a redirection unit 134 forsending one or more MAP signaling messages to redirect roamer's traffic.HPMN 102's deployed detection unit 132 and redirection unit 134 arecollectively referred to as ITR module 130 for providing the ITRSsolution, in accordance with various embodiments of the presentinvention. It will be apparent to a person skilled in the art, thatdifferent functions are associated with detection unit 132 andredirection unit 134 only for exemplary purposes. Any functionalproperty of any of the two will be associated with ITR module 130. Inother words, any function that is to be performed by either detectionunit 132 or redirection unit 134 is alternatively capable of beingperformed by ITR module 130 alone.

In another embodiment of the present invention, ITR module 130 activelyintercepts the signaling from STP-V1 116 or from international STP1 118in an in-signaling path mode. In this case, the operator in first VPMN104 may configure STP-V1 116 to assist in exchange of one or moreregistration cancellation message (i.e. MAP CancelLocation), and one ormore registration messages (i.e. MAP LUP) between HPMN 102 and firstVPMN 104. In one embodiment of the present invention, a firstregistration cancellation message is a CancelLocation message sent fromHLR-H 110 to cancel the registration of roamer 106 with first VPMN 104.In another embodiment of the present invention, one or more registrationmessages are LUP messages that are sent on behalf of roamer 106. In oneembodiment of the invention, all signals exchanged through STP-V1 116are SCCP/TCAP based signals. Such “active” monitoring is hereinafterreferred interchangeably as in-signaling mode. In the in-signaling mode,ITR module 130 is deployed on roaming SS7 path by configuring STP-V1 116to route international roaming SCCP traffic through ITR module 130. Inone embodiment of the present invention, the operator in first VPMN 104configures STP-V1 116 to provide a primary routing (i.e. via ITR module130) and a secondary routing (i.e. via VLR-V1 112) of incoming andoutgoing signaling messages. The secondary routing provides a redundantpath for routing of traffic in case of failure of primary routing.Hence, the monitoring or probing of the TR attempt is performed in twomodes, passive monitoring or active monitoring of the signals.

It will be apparent to a person skilled in the art that in order toavoid looping of routing of messages, involved in the TR process, theITR can be either performed using a Translation Types (or tables) (TT)or using an Message Transfer Part (MTP) routing. This involvesinternational STP Signal Point Code (SPC) and Switching/Roaming SPCdepending on the network setup in VPMN(s). In case the TT is used, theoperator in first VPMN 104 configures STP-V1 116 and ITR module 130 forboth incoming and outgoing international SCCP signaling messages.Considering the second technique of using MTP routing, the operator infirst VPMN 104 configures STP-V1 116 to send an incoming message, with aNumbering Plan (NP) as E.214 and CdPA Destination Point Code (DPC) asITR module 130. Various other embodiments involved in the TT and the MTProuting techniques have already been described in the previous ITRfiling.

The present invention provides various embodiments where the competitorVPMN VLR (i.e. VLR-V2 114), instead of HLR-H 110, aborts theregistration attempt of the inbound roamer at the competitor VPMN. Asthe competitor VPMN VLR aborts the registration attempt, it is referredto as competitor VLR abort. FIG. 2 is a flowchart for controllingtraffic of the roamer of HPMN in the VLR error based approach, inaccordance with an embodiment of the invention. At step 202, aredirection unit coupled to a first VPMN detects a registration attemptof a roamer at a second VPMN, upon receipt of a first registrationcancellation message of one or more registration cancellation messages,which the HPMN sends. In an embodiment of the present invention, whenroamer 106 makes a registration attempt at second VPMN 108, VLR-V1 112receives a MAP CancelLocation message from HPMN 102. ITR module 130detects this registration attempt by monitoring (i.e. actively orpassively) the MAP CancelLocation message. Thereafter, at step 204, theredirection unit sends one or more registration messages to the HPMNthat causes the HPMN to send a registration response message to a VLRassociated with the second VPMN, to thwart the registration attempt ofthe roamer at the second VPMN. In one embodiment of the presentinvention, ITR module 130 sends a MAP Location Update message (i.e. LUP)on behalf of first VPMN 104 to HLR-H 110 that causes HLR-H 110 to send aregistration response message, such as LUP-ACK or MAP CancelLocationmessage or LUP reject error to second VPMN 108. Since this LUP messageis sent on behalf of roamer 106 giving an impression that roamer 106 isin first VPMN 104, it is hereinafter referred to as “fake” LUP message.Signaling response messages such as CancelLocation message or LUP rejecterror, causes HPMN 102 to abort the registration attempt of roamer 106at second VPMN 108.

In another embodiment of the present invention, HLR-H 110 may requirefirst VPMN 104 to authenticate the inbound roamers of HPMN 102, prior toinitiating the registration process between HPMN 102 and first VPMN 104.In such a case, the operator in first VPMN 104 may perform anauthentication (using a Send Authentication Information (SAI) message)of the inbound roamer, prior to sending the LUP message to HLR-H 110. Inan embodiment of the present invention, roamer 106's handset gets stuckin second VPMN 108, either during its registration attempt with secondVPMN 108, or after its successful registration with second VPMN 108.This may happen due to the implementation of the ITRS solution at firstVPMN 104. In such cases, after the authentication and synthetic or“fake” registration is done, the redirection unit at step 206facilitates the roamer's mobile communication. In other words,redirection unit 134 enables roamer 106 to make and receive callsdespite being stuck earlier. FIGS. 7A, 7B, and 7C, and FIGS. 8A, 8B, 8Cdescribe various embodiments that cause the roamer's handset to getstuck in the second VPMN, and the mechanism used to handle such cases.

In one embodiment of the present invention, ITR module 130 in first VPMN104 exploits the racing condition of its fake LUP messages and thecompetitor network's (i.e. second VPMN 108) ongoing location update withHLR-H 110. Therefore, ITR module 130 is able to create HPMN 102 TR onroamer 106, according to its preferences, irrespective of whether HPMN102 has the TR solution deployed at its network. The ITRS solution alsohas a dependency of TR, e.g. on mobile handsets and some VLR/VMSC/BaseStation Subsystem (BSS) versions. As per Global System for Mobilecommunication (GSM) standard, the CancelLocation message to a previousVPMN (triggered by a new location update) is an independent process froman ongoing location update process. In addition, the GSM standard doesnot make sending of CancelLocation message time dependent. In otherwords, HPMN 102 may opt to send the CancelLocation message to theprevious VPMN (i.e. network with which roamer 106 was earlierregistered) before or after the completion of the ongoing locationupdate process. In an embodiment of the present invention, HPMN HLR(i.e. HLR-H 110) sends the CancelLocation message immediately, upon areceipt of a new LUP message. In another embodiment of the presentinvention, some HPMN HLR (e.g. some Nokia™ HLR versions) issues theCancelLocation message to the ITR deploying VPMN (i.e. first VPMN 104)only after the completion of location update process of roamer 106 withthe competitor VPMN (i.e. second VPMN 108). Therefore, the ITRS solutionalso depends upon the HPMN HLR implementation.

In an embodiment of the present invention, upon receiving a new LUPmessage in the middle of an ongoing location update transaction, someHPMN HLRs issue CancelLocation message to the ongoing location updatetransaction, while some HPMN HLR aborts the ongoing location updatetransaction. As a result, the ITRS solution indirectly also depends onthe competitor VPMN VLR (i.e. VLR-V2 114) implementation, i.e. when theyare not following the GSM standard. In an embodiment of the presentinvention, the competitor VPMN VLR aborts the ongoing LUP transactionwhen it receives the CancelLocation message on roamer from the HPMN HLR.However, some VLR versions do not follow the GSM standard, and hence donot abort the ongoing LUP transaction. In addition, upon receiving theHPMN HLR abort for the ongoing LUP transaction, most VLR/VMSC/BSS willgenerate a network failure error at an air interface (which is receivedat roamer 106's handset) according to the GSM standard. However, someVLR/VMSC/BSS combinations again do not follow the GSM standard and hencedo not generate a network failure error at the air interface. Therefore,ITR retention success depends upon both the HPMN HLR, and the competitorVPMN VLR, in addition to the normal dependencies of the TR.

Like TR, the ITRS solution is based on a statistical distributionframework. Usually, retention success can be in the range of 10% to 20%.The retention success is defined as the percentage of departing roamersto competitor network retained back.

${{Retention}\mspace{14mu}{success}} = {\frac{\begin{bmatrix}{{Retained}\mspace{14mu}{roamers}\mspace{14mu}{departing}\mspace{14mu}{to}} \\{{competitor}\mspace{14mu}{network}}\end{bmatrix}}{\left\lbrack {{Departing}\mspace{14mu}{roamers}\mspace{14mu}{to}\mspace{14mu}{the}\mspace{14mu}{competitor}\mspace{14mu}{network}} \right\rbrack}\%}$

Despite all these dependencies, the ITRS still can provide a significantrevenue increase on inbound roaming revenue due to its statisticalsuccess.

As described earlier, the present ITRS solution provides a VLR errorbased approach that causes the competitive VPMN VLR abort due to the ITRattempt from first VPMN 104, when roamer 106 attempts to register withthe competitor VPMN (i.e. second VPMN 108). FIG. 3 represents a flowdiagram for providing enhanced location based ITR to cause thecompetitor VLR abort in the VLR error based approach, in accordance withan embodiment of the present invention. In case roamer 106 leaves theVPMN deploying ITR module 130, ITR module 130 continues to send the fakeLUP messages to HLR-H 110. To avoid such a situation, the enhancedlocation based ITR is performed.

Roamer 106 may attempt to (or is forced to attempt to) register withsecond VPMN 108 due to one or more reasons mentioned above. Hence, atstep 302, VLR-V2 114 sends an LUP message to HLR-H 110. Detection unit132 can deduce that roamer 106 is attempting to register with secondVPMN 108 when it detects no new registration message sent from firstVPMN 104; and it still detects receipt of one or more registrationcancellation messages (i.e. CancelLocation message) at first VPMN 104. Afirst registration cancellation message of one or more registrationcancellation messages is sent directly to VLR-V1 112, while thesubsequent registration cancellation messages are tapped at ITR module130. Therefore, at step 304, HLR-H 110 sends a MAP CancelLocationmessage to VLR-V1 112, in order to abort roamer 106's registration withfirst VPMN 104. Thereafter, at step 306, HLR-H 110 sends another MAPCancelLocation message that is tapped by ITR module 130. In order toperform ITR, in accordance with an embodiment of the present invention,ITR module 130 sends one or more registration messages (i.e. fake LUPmessage) to HLR-H 110, upon detecting a receipt of the CancelLocationmessage at detection unit 132. This causes HLR-H 110 to send an abortmessage, such as CancelLocation to VLR-V2 114, which returns anacknowledgement, such as TCAP abort to HLR-H 110. This aborts roamer106's registration with second VPMN 108 generating a network failure onroamer 106's handset. This call flow later explains in detail theprocess of causing HLR-H 110 to send the abort message and receivesubsequent response from second VPMN 108's VLR.

In another embodiment of the present invention, while performing theenhanced location based ITR attempt, ITR module 130 sends a searchrequest message upon receipt of the CancelLocation message from HLR-H110. Various embodiments of sending the search request message to a lastknown VMSC of roamer 106 to collect location area information of roamer106 are similar to the previous ITR filing. However, if there are errorsto the search request message, then the current network and the countryof roamer 106 cannot be identified. To avoid this problem, anotherembodiment of performing location based ITR attempt is now described.Referring to FIG. 3, after the first CancelLocation message is receivedat VLR-V1 112, ITR module 130 can send a routing request immediately,prior to sending the fake LUP message to HLR-H 110. In one embodiment ofthe invention, the routing request is a MAP Send Routing Information forShort Message (SRI-SM) message. In another embodiment of the invention,the routing request is an SRI message. In yet another embodiment of theinvention, the routing request is an Any Time Interrogation (ATI)message. The SRI-SM message can be sent on a Mobile StationInternational Subscriber Directory Number (MSISDN) of roamer 106. Hence,at step 308, ITR module 130 can send the SRI-SM message to HLR-H 110, inorder to retrieve a VMSC address of roamer 106.

In an embodiment of the present invention, in case HLR-H 110 requiresfirst VPMN 104 to authenticate roamer 106 with his HPMN 102, first VPMN104 can initiate an authentication procedure, prior to sending the fakeLUP message to HLR-H. In another embodiment of the present invention,first VPMN 104 is required to initiate the authentication procedure incase roamer 106 was registering with first VPMN 104 for the first time.At step 310, ITR module 130 sends one or more authentication messages,such as Send Authentication Information (SAI) request to HLR-H 110,prior to sending one or more registration messages (i.e. fake LUPmessages) to HLR-H 110. In yet another embodiment of the presentinvention, if the operator in HPMN 102 is determined to be present in awhitelist of the operator in first VPMN 104, ITR module 130 sends theSAI request message to HLR-H, in order to authenticate roamer 106 withhis HPMN 102. Thereafter, at step 312, HLR-H 110 returns an SAI-ACKmessage that indicates successful authentication of roamer 106. In anembodiment of the present invention, the SAI-ACK message consists of oneor authenticating parameters, such as triplets and quintuplets, used forauthenticating roamer 106 with his HPMN 102. Steps 308 to 312 are shownin dashed line, as the operator in first VPMN 104 may optionally performthese steps, depending upon its implementation requirement andfeasibility.

For each registration cancellation message detected, ITR module 130sends one or more fake LUP messages within a first pre-defined intervalof time (T0) until one registration message is recorded as a successfultransaction. Hence, at step 314, ITR module 130 attempts to redirect thetraffic to first VPMN 104 by sending one or more fake LUP to HLR-H 110.T0 is the time interval required for completion of location updateprocess at HLR-H 110. However, all the fake LUP messages from ITR module130 need to be sent within a second pre-defined time interval (T1),and/or until a re-registration threshold is reached. The T1 timeinterval is a re-registration timer that indicates the time left toperform an ITR attempt for a departing roamer. Various otherinterpretations of T0 and T1 time interval are similar to the previousITR filing.

As explained earlier, ITR module 130 attempt the ITR by sending variousMAP messages, such as, but not limited to, SRI-SM message, SAI message,and fake LUP message. In one embodiment of the present invention ITRmodule 130 may send these messages using one or more GT(s) for eachCancelLocation message received at VMSC/VLR-V1 112. The GT used forsending these messages may be a new GT allocated to ITR module 130 bythe operator in first VPMN 104. However, in this case, ITR module 130needs to inform all its roaming partners regarding the new GT being usedfor performing any kind of TR attempt, as per IR 21 roaming guideline.This ensures that the roaming partners of first VPMN 104 configure theirrespective STPs for appropriately routing the signaling messages on thenew GT to ITR module 130.

However, some VPMN operators may not like to disclose to theircompetitor VPMN or HPMN operator that they are performing any kind of TRagainst them. Also, some VPMN operators may not have a spare GT toallocate to ITR module 130. In either of these cases, ITR module 130 mayuse a GT of VLR-V2 114 after modifying it. The modified VLR-V2 GT may begenerated by adding one or more trailing digits to the VLR-V2 GT. Inother words, ITR module 130 post-fixes the existing VLR-V2 GT (usuallyless than 15 digits) to create a new post-fixed GT of 15 digits or less.Also, the operator in first VPMN 104 configures STP-V1 116 to route allincoming signaling messages with CdPA as the new post-fixed GT to ITRmodule 130. Since, the STPs usually route the GTs based on theirprefixes instead of postfixes, it helps the operator in first VPMN 104to avoid informing other competitor networks (and even HPMN) of thispost-fixed GT and thus remain unknown while attempting any kind of TR.This at least makes it difficult for HPMN and other VPMN operators todiscover its ITR module 130.

In one embodiment of the present invention, ITR module 130 sends thefake LUP message upon a receipt of an SRI-SM ACK message. In anotherembodiment of the present invention, ITR module 130 sends the fake LUPmessage to HLR-H 110, without waiting for the SAI-ACK message (i.e. atstep 312). In yet another embodiment of the present invention, ITRmodule 130 sends the fake LUP message immediately after sending theSRI-SM message (i.e. after step 308) without waiting for the SRI-SM ACKmessage. If HLR-H 110 retrieves a VMSC (or VLR) location of roamer 106immediately from a new network location update even before it iscompleted, then the SRI-SM ACK message will return roamer 106's currentVMSC. Once the current VMSC of roamer 106 is retrieved, and are-registration counter corresponding to an International MobileSubscriber Identity (IMSI) of roamer 106 is at threshold, then ITRmodule 130 does not attempt the ITR any further, however, it mayoptionally provide Value Added Service (VAS) to roamer 106. Someexemplary VAS may be, but not limited to, a Winback SMS, and a PrepaidLocal Number service.

In an embodiment of the present invention, ITR module 130 blacklistsHLR-H 110 for a pre-defined time interval in absence of a response or inpresence of an error message (e.g. system failure or unexpected datavalue or data missing etc) to the routing request (SRI-SM) for aconfigurable number of times from HPMN 102. This blacklisting restrictsITR module 130 from sending any further SRI-SM query before each fakeLUP message. In other words, when CancelLocation message on roamer 106is received from HLR-H 110, and if this HLR is blacklisted due to any ofthe above reasons, ITR module 130 issues fake LUP messages (i.e. at step314) without sending any routing request (SRI-SM) prior to it.

In another embodiment of the present invention, when a VMSC is returnedin the SRI-SM ACK, ITR module 130 may determine whether this VMSC insecond VPMN 108 is a non-ITR attempting network, after applying someapplication logics of pre-defined criteria on the response. Thereafter,ITR module 130 will not send any SRI-SM message prior to subsequent fakeLUP messages including the follow-on one, if the fake LUP message isissued after the SRI-SM ACK, to HLR-H 110. In other words, the ITRattempt on the departing roamer 106 will not be abandoned.

In yet another embodiment of the present invention, ITR module 130blacklists HPMN 102 for a pre-defined time interval, in case HLRassociated with HPMN 102 fails to return any VMSC address (i.e. in theSRI-ACK message) in response to the SRI message (i.e. from ITR module130). This blacklisting allows the operator in first VPMN 104 torestrict ITR module 130 from sending further SRI messages to HLR-H 110.In other words, ITR module 130 issues fake LUP messages without anyrouting request (i.e. SRI) prior to it. In an exemplary case, if theoperator in HPMN 102 has deployed a Short Message Service (SMS) relaymechanism for relaying SMS always through HPMN 102, irrespective ofroamer 106's current location, HPMN 102 will always return its ownaddress to ITR module 130 in its SRI-ACK message instead of VMCSaddress. In such a case, ITR module 130 will blacklist HPMN 102 fromissuing any routing request (SRI-SM) prior to fake LUP messages.

In an embodiment of the present invention, an error message is returnedin response to ITR module 130's fake LUP message indicating unknownsubscriber, Roaming Not Allowed (RNA), Operator Determined Barring(ODB), RNA in location area (due to restriction, regional servicesubscription, national roaming and the like). In this embodiment, ITRmodule 130 can blacklist the roamer 106's IMSI for subsequent fake LUPmessages, until the IMSI is registered in first VPMN 104 again, thusabandoning the ITR attempt.

In another embodiment of the present invention, VLR-V2 114 may not abortthe location update transaction of roamer 106 at second VPMN 108, incase roamer 106's registration with second VPMN 108 is successfullycompleted. In other words, when HLR-H 110 sends a CancelLocation messageto VLR-V2 114, VLR-V2 114 will not acknowledge this message and willretain roamer 106 on second VPMN 108. This effects the mobilecommunication of roamer 106, as HLR-H 110 has the ITR's fake locationaddress (as VMSC/VLR address) registered in its database and VLR-V2 114has the knowledge that roamer 106 is still registered with second VPMN108. Due to this, although roamer 106 is able to initiate MobileOriginated (MO) activities, he is unable to perform any MobileTerminated (MT) activities. In addition, when ITR module 130 sends theSRI message to HLR-H 110, prior to sending the fake LUP message, theVMSC/VLR address of second VPMN 108 is returned in the SRI-ACK messageto ITR module 130. However, in an embodiment of the present invention,if HLR-H 110 does not issue any registration response message, such asCancelLocation, to VLR-V2 114, even after the fake LUP message is sentfrom ITR module 130 to HLR-H 110, ITR module 130 can blacklist theVMSC/VLR (i.e. returned in the SRI-ACK message). This blacklisting ofthe VMSC/VLR ensures that first VPMN 104 will not perform any furtherITR attempt on roamer 106 in such case.

In order to avoid such a situation, ITR module 130 may opt to send oneor more fake LUP messages (i.e. at step 314) successively for apre-defined number of times to HLR-H 110. This causes either HLR-H 110to issue an abort message in order to abort the ongoing LUP transactionof roamer 106 with second VPMN 108, or forces VLR-V2 114 to abort theongoing LUP transaction upon receiving the CancelLocation message fromHLR-H 110 for the first set of fake LUP messages. Subsequently, at step316, HLR-H 110 successfully completes the LUP transaction with firstVPMN 104. Therefore, first VPMN 104 is able to retain roamer 106 usingthe ITRS solution deployed at first VPMN 104. In an embodiment of thepresent invention, the successful LUP transaction implies exchange ofother necessary messages, such as a MAP ISD and a MAP ISD-ACK (accordingto the underlying protocol) also to be successfully exchanged betweenfirst VPMN 104 and HLR 110.

Due to one or more consecutive fake LUP messages (i.e. at step 314) andsuccessful LUP (i.e. at step 316), HLR-H 110 subsequently at step 318,sends an abort message, such as a CancelLocation message to VLR-V2 114,to abort the LUP transaction of roamer 106 at second VPMN 108.Thereafter, at step 320, VLR-V1 114 returns an acknowledgement message,such as TCAP abort to HLR-H 110. Hence, ITR module 130 causes thecompetitor VLR to abort the LUP transaction with the competitive VPMN.Finally, at step 322, VLR-V2 114 sends a failure message, such asnetwork failure to roamer 106's handset. Examples of network messagesfrom HPMN 102 to second VPMN 108, resulting in a radio message to roamer106 indicating the network failure are, but not limited to, MAP U/PABORT, MAP_CLOSE, TCAP abort, and system failure, depending onimplementation of the HPMN HLR (i.e. HLR-H 110) and competitive VPMN VLR(i.e. VLR-V2 114).

In an embodiment of the present invention, even after sending one ormore consecutive fake LUP messages, detection unit 132 does not detectany CancelLocation message from HLR-H 110 and intended for VLR-V2 114,within the second pre-defined time interval T1 or within there-registration threshold. In this embodiment, if the fake LUP messageis preceded with the routing request message such as SRI-SM, ITR module130 can blacklist HLR-H 110 and VMSC/VLR-V2 114, and hence abandoningthe ITR attempt.

In another embodiment of the present invention, if the ITR attempt isfinished (due to the threshold of timers and counters), although not yetsuccessful, then ITR module 130 may send one final SRI-SM to HLR-H 110to retrieve a VMSC address stored at HLR-H 110. In such a case, HLR-H110 returns an address of ITR module 130 due to the last sent fake LUPmessage. Thereafter, ITR module 130 can perform one of the following:

-   -   1. ITR module 130 may issue a PurgeMS message to HLR-H 110 on        the IMSI of departing roamer 106. This results in HLR-H 110 to        have no VMSC/VLR address of roamer 106. Thus, in case of any MT        call or SMS, when a routing request is received at HLR-H 110,        and HLR-H 110 has no VLR/VMSC address, it will return a message        that indicates an unattached mobile (i.e. VMSC/VLR address of        roamer 106 is unknown).    -   2. ITR module 130 may reset the counters and expiration timers        for departing roamer 106. In this case, when ITR module 130        detects a new CancelLocation message from HLR-H 110 (maybe due        to roamer 106's mobile activities like location area changes, or        any MO activities), ITR module 130 will have another chance to        redirect roamer 106 back to first VPMN 104. However, in case of        incoming calls, ITR module 130 will receive HLR-H 110's Provide        Roaming Number (PRN) request. ITR module 130 will return ‘Absent        Subscriber’ message to HLR-H 110, as an acknowledgement to the        PRN request message. In case of an incoming SMS, when a Forward        SMS is received at ITR module 130 from HLR-H 110, ITR module 130        will send a Forward SMS ACK with ‘Absent Subscriber’ message to        HLR-H 110, so that subsequent incoming calls and SMS do not come        to ITR module 130.

Another embodiment of the present invention provides additional criteriafor handling a special case of the ITRS solution. In order to handlethis special case, the operator in first VPMN 104 defines aconfiguration distribution control profile among inbound roamers of eachHPMN. The configuration distribution control profile supports indecision of performing the ITR attempt. As an exemplary case, ITR module130 may activate the configuration distribution control profile on eachHPMN at different time bands. The configuration distribution controlprofile for each HPMN is defined based on the following, but not limitedto, one or more parameters:

-   -   1. Unique inbound roamers: For example, no more than 15% of        unique departing inbound roamers from Vodafone™ United Kingdom        (UK) are subjected to ITR attempts.    -   2. Inbound TR attempts: For example, no more than 15% of        departing inbound roamers from Vodafone™ United Kingdom are        subjected to ITR attempts.    -   3. Inbound TR success: For example, no more than 30% of        departing inbound roamers (i.e. unique or any) from Vodafone™        United Kingdom ITR are subjected to ITR success.

In one embodiment of the present invention, a configurable countermeasures these one or more parameters in the configurable distributioncontrol profile. In other words, the distribution measure can beperformed for the configurable counter of the corresponding count ineach of the above one or more parameters. For example, if thedistribution control is on ITR attempts and the configurable counter isset to 10, then the percentage will be measured for every 10 ITRattempts. Therefore, the operator in first VPMN 104 can define

${{Success}\mspace{14mu}{rate}} = \frac{{Total}\mspace{14mu}{ITR}\mspace{14mu}{success}\mspace{14mu}{counter}}{{Total}\mspace{14mu}{redirection}\mspace{14mu}{counter}}$

In another embodiment of the invention, if HLR-H 110 has fraud controlin a way that it discards a fake LUP message from ITR module 130, orsimply new registration attempts of roamer 106 during another locationupdate transaction of roamer 106, ITR module 130 blacklists HLR-H 110from future ITR attempts. In yet another embodiment of the invention,the enhanced location-based ITR mechanisms can even be applied toperform network selection for departing roamers going to a new VPMN inanother country. In case, the roamer goes back to the home country, theITR attempt is abandoned. However, it is possible to select networks inthe home country, when the operator in HPMN allows the roamer to roam inthe home country (i.e. national roaming). In this embodiment of theinvention, ITR module 130 attempts to perform the ITR to a third VPMNwhen the attempt to perform the ITR to first VPMN 104 is unsuccessful.This can be useful for a group alliance, i.e., when the third VPMN is apreferred network to first VPMN 104 as compared to second VPMN 108 whichis a non-preferred network for first VPMN 104. Therefore, all thespecial handling mechanisms defined for ITR mechanism within the countrycan be similarly applied for the ITR outside the country. Hence, theITRS solution allows the VPMN operator to redirect the roamer to anynetwork of his choice by identifying location of the roamer.

FIG. 4 represents a flow diagram for providing location recovery basedITR in the VLR error based approach, in accordance with an embodiment ofthe present invention. In case roamer 106 leaves the country of firstVPMN 104 that is deploying ITR module 130, ITR module 130 attempts toidentify the new location of roamer 106. The possible change in theregistration of roamer 106 is inferred when an LUP message is receivedat HPMN 102 from second VPMN 108. At step 402, VLR-V2 114 sends the LUPmessage to HLR-H 110. VLR-V2 114 sends this LUP message, after roamer106 attempts to (or is forced to attempt to) register with second VPMN108. Thereafter, at step 404, ITR module 130 detects a possible changein registration of roamer 106, upon receipt of a CancelLocation messageat first VPMN 104 from HLR-H 110. In this case, the first CancelLocationmessage received at first VPMN 104 is held at ITR module 130. ITR module130 may identify a blind spot in first VPMN 104 due to which roamer 106has attempted to register with second VPMN 108. Therefore, at step 406,ITR module 130 sends a Provide Subscriber Information (PSI) message asthe subscriber information message to VLR-V1 112 before relaying thefirst registration cancellation message (i.e. CancelLocation) to VLR-V1112 at step 408. Thereafter, VLR-V1 112 may page roamer 106 inanticipation of a reply from roamer 106 indicating a current celllocation in first VPMN 104. Thereafter, at step 410, VLR-V1 112 sends anacknowledgement message, such as PSI-ACK, returning the location ofroamer 106. In another embodiment of the present invention, or in casethere is no response to the paging, VLR-V1 112 simply returns the lastknown cell location (i.e., the cell where roamer 106 was previouslylocated) to ITR module 130. All these variations intend to gain a roughidea of the blind spots where the roamer was about to be lost from firstVPMN 104. In yet another embodiment of the present invention, ITR module130 may relay the CancelLocation message (at step 408) to VLR-V1 112,even before it receives an acknowledgment to the PSI message. It will beapparent to a person skilled in the art, that the PSI-ACK message willbe processed independent of the current ITR attempt.

Further, at step 412, ITR module 130 continues the ITR attempt bysending fake LUP messages to HLR-H 110. Upon exchange of some standardMAP messages between HLR-H 110 and ITR module 130, at step 414, theregistration process completes successfully with HLR-H 110. Thecompletion of successful registration process between first VPMN 104 andHPMN 102 causes the competitor VLR abort. Hence, at step 416, HLR-H 110sends a CancelLocation message to VLR-V2 114, to abort the registrationattempt of roamer 106 at second VPMN 108. Thereafter, at step 418,VLR-V2 114 acknowledges the abort, by returning a TCAP abort message toHLR-H 110. This causes VMSC/VLR-V2 114 to generate a Network Failureerror (#17) at roamer 106's handset, at step 420.

As described earlier in FIG. 1, there may be a case where the operatorin HPMN 102 deploys a TR solution against one or more VPMN(s). FIG. 5represents a flow diagram for performing the ITR in conjunction withcountering the TR attempt initiated by the HPMN in the VLR error basedapproach, in accordance with an embodiment of the present invention. Inthis embodiment, we have assumed that HPMN 102 is deploying the TRsolution against first VPMN 104. The possible change in the registrationof roamer 106 is inferred when an LUP message is received at HPMN 102from second VPMN 108. At step 502, HLR-H 110 receives the LUP messagefrom VLR-V2 114. Thereafter, at step 504, detection unit 132 detects apossible change in registration of roamer 106, upon receipt of aCancelLocation message at first VPMN 104 from HLR-H 110. Detection unit132 can therefore deduce that roamer 106 is attempting to register withsecond VPMN 108. At step 506, HLR-H 110 sends another CancelLocationmessage that is tapped by ITR module 130. Further, at step 508, ITRmodule 130 attempts to redirect the inbound roamer's traffic to firstVPMN 104 by sending fake LUP messages from ITR module 130 to HLR-H 110.In this embodiment of the present invention (as explained earlier inFIG. 1), the operator in first VPMN 104 deploys an anti-TR unit tocounter the TR attempts from HPMN 102, based on one or moreacknowledgement messages sent by HPMN 102 in response to the fake LUPmessages from first VPMN 104. At step 510, HPMN 102 (i.e. a TR unitdeployed at HPMN 102, or HLR-H 110 itself) sends an acknowledgementmessage, such as an LUP reject error message to ITR module 130. Theexamples of error in the LUP reject error message include systemfailure, Unexpected Data Value (UDV), Missing Data (MD) and the like. Inanother embodiment of the present invention, the acknowledgement messageis an LUP abort error message. In case any of the two messages arereceived as the acknowledgement messages, ITR module 130 continues tosend fake LUP messages, until a successful LUP transaction is completedor a threshold (e.g. T0) is reached. In an embodiment of the presentinvention, ITR module 130 sends the fake LUP message to HLR-H 110, up tofour times. Based on the attributes in the acknowledgement message (i.e.at step 510), ITR module 130 decides whether to apply anti-TR solutionor to abandon the ITR attempt.

The acknowledgement message may contain a UDV, Roaming Not Allowed(RNA), Roaming Restricted (RR), System Failure (SF), MD or any othererror as the attribute. According to the configuration of the ITRdeploying VPMN operator, in case the LUP reject error contains the UDV(which is an IR 73 compliant TR error) from a dedicated HPMN GT, ITRmodule 130 may abandon its current ITR attempt. An HPMN GT is considereddedicated for the TR using UDV, if it is the only GT used for sendingUDV in the TR solution at HPMN 102. However, if the LUP reject error isSF or MD (which are non-compliant to IR 73), then the anti-TR solution(i.e. anti-non-compliant TR solution) may be applied along with thecurrent ITR attempt. The anti-TR unit is referred to asanti-non-compliant TR solution in a VPMN if the anti-TR unit is onlyapplied to non-compliant errors (such as system error and missingvalues) used by an HPMN TR solution. The integrated ITR and Anti-TRsolution works for both active monitoring and passive monitoring mode.

In case the attribute in the acknowledge message is RNA or RR, the ITRSsolution is modified in a way that ITR module 130 immediately retriesuntil a successful transaction or a threshold is reached, as it can bededuced that HPMN 102 is applying TR on roamer 106. In this case, thecurrent ITR attempt may be abandoned. This solution works for bothactive and passive mode ITR. To confirm that HPMN 102 is performing TR,the decision to abandon the ITR might be concluded only after RNA isreceived in the acknowledgement message for a configurable number ofsuccessive times of the fake LUP messages on roamer 106.

Based on the acknowledgment received in LUP reject error message, atstep 512, ITR module 130 once again sends a new fake LUP message to HPMN102. Thereafter, at step 514, HPMN 102 completes the registrationprocess with first VPMN 104 to allow roamer 106 to register with firstVPMN 104. This causes HPMN 102, at step 516, to send a CancelLocationmessage to VMSC/VLR-V2 114. VMSC/VLR-V2 114 at step 518 returns anacknowledgement message, such as a TCAP abort to HPMN 102. Finally, atstep 520, VMSC/VLR-V2 114 sends a network failure at roamer 106'shandset.

In an embodiment of the present invention, an Over The Air (OTA) basedapproach may exist, that either modifies a preferred PLMN list orspecial SIM entries to initiate network reselection by roamer 106'shandset. The anti-TR unit may deal with this OTA based caseindependently, since it does not have to be tied with location updatetransaction (or process). In another embodiment of the presentinvention, in the active monitoring mode, the ITR attempt can becombined with a Gateway Location Register (GLR) based technology. TheGLR based technology uses a GLR unit deployed in a hosting location byan international SS7 carrier or a common carrier for multiple VPMNoperators. In one embodiment of the present invention, the GLR unit canbe integrated with the ITR module in a same platform in such a way thatthe GLR can either be independently applied outside the ITR ordependently applied inside the ITR. In an embodiment of the presentinvention, after the inbound roamer of TR applying HPMN (i.e. HPMN 102)has successfully registered with first VPMN 104, the GLR unit can alsoperiodically issue several fake LUP messages on the retained roamer'sIMSI in order to distort the HPMN distribution profile on the roamers.This will increase the chance of more roamers of HPMN 102 registering atfirst VPMN 104.

However, this GLR solution will not be effective against an HPMN TRsolution that is based on a distribution control of unique roamersacross VPMNs (i.e. in a visiting country) or on a percentage of LUPreject error for individual VPMN in a visiting country. In oneembodiment of the present invention, this solution allows the operatorin first VPMN 104 to retain initially registered roamers on its network.However, it does not consider a case when new roamers attempt toregister with first VPMN 104. Hence, in order to allow more inboundroamers to register with first VPMN 104, the operator in first VPMN 104can dynamically swap in and swap out the retained roamers using a GLRcaching mechanism. In one embodiment of the present invention, theoperator in first VPMN 104 may opt to retain, via the GLR caching, theinbound roamers that generate more revenues while roaming in first VPMN104, as compared to those that do not generate similar revenues. Thiscauses the location update of inbound roamers, who are not cached by theGLR, to go back to HPMN 102 and be subjected to possible TR. Therefore,the operator in first VPMN 104 will achieve better revenues for theretained roamers without affecting the HPMN TR distribution mechanism(unless the HPMN TR distribution mechanism is itself based on revenuedistribution).

Alternatively, ITR module 130 can send one or more fake LUP messages ona departing roamer's IMSI, using the VMSC/VLR address obtained from theSRI-SM, when it is known that the departing roamer has registered with acompetitor network (i.e. second VPMN 108). This fake LUP message willnot affect the services of the departing roamer in second VPMN 108, asthe VLR/VMSC address used is the actual VMSC/VLR address of second VPMN108. In an embodiment of the present invention, ITR module 130 sends thefake LUP messages using VLR/VMSC address of second VPMN 108, to HPMN 102for a pre-defined number of times (i.e. configured by the operator infirst VPMN 104). The intention is to create a fake distribution image atHPMN TR solution, so that HPMN 102 assumes that the competitor VPMN(i.e. second VPMN 108) has exceeded its share of traffic distribution.This results in HPMN 102 re-distributing the share of roamers to the ITRdeploying first VPMN 104. Since, first VPMN 104 has sent the fake LUPmessage to HPMN 102 using the VMSC/VLR address of second VPMN 108, HPMN102 will send a response message to second VPMN 108, which will beaborted by second VPMN 108.

In one embodiment of the invention, second VPMN 108 may also deploy theITRS solution for redirecting roamer 106's traffic to its network. Inthis embodiment, second VPMN 108 may optionally include an ITR module,which may be similar to ITR module 130. FIG. 6 represents a flow diagramfor performing the ITR to counter an ITR attempt from a competitornetwork, in accordance with an embodiment of the present invention. Thisembodiment assumes that roamer 106 (i.e. in this embodiment) isinitially registered with second VPMN 108. However, when roamer 106attempts to register with first VPMN 104, at step 602, VMSC/VLR-V1 112sends an LUP message to HLR-H 110. This causes HLR-H 110 to issue aCancelLocation message to VMSC/VLR-V2 114 in second VPMN 108, at step604. Thereafter, at step 606, the ITR module in second VPMN 108 sends afake LUP message to HLR-H 110. At step 608, HLR-H 110 sends aCancelLocation message to first VPMN 104 (i.e. received at VLR-V1 112).Thereafter, at step 610, VLR-V1 112 returns a TCAP abort message toHLR-H 110, to abort roamer 106's registration attempt at first VPMN 104.However, upon receiving the CancelLocation message (i.e. at step 608),ITR module 130 can deduce the presence of the ITR module at second VPMN108 that is performing an ITR attempt in second VPMN 108 to retain itsinbound roamer from leaking to first VPMN 104. Hence, to thwart secondVPMN 108's ITR attempt, at step 612, ITR module 130 sends a fake LUPmessage three or more times in succession to defeat second VPMN 108'sITR attempt. Finally, at step 614, HPMN 102 successfully completes theregistration process with first VPMN 104, to allow roamer 106 toregister at first VPMN 104. As a successful transaction is recorded atHLR-H 110, the ITR module in second VPMN 108 perceives that the handsetis in manual mode or second VPMN 108 has no coverage, and therebyabandoning any further ITR attempts.

In an embodiment of the present invention, roamer 106's handset may evenget stuck after ITR module 130 attempts for four times and still roamer106 is not able to register back to first VPMN 104. Since, HLR-H 110knows an address of ITR module as the VMSC/VLR address of first VPMN104, roamer 106 will not be able to receive any calls and SMS on hishandset. In an embodiment of the present invention, ITR module 130removes its own address from HLR-H 110, by sending a registrationlocation detached message, such as a MAP PurgeMS to HLR-H 110. Inanother embodiment of the present invention, some of the HLRs send aCancelLocation message to first VPMN 104 after roamer 106 issuccessfully registered with second VPMN 108. In this embodiment, uponreceiving the CancelLocation message at first VPMN 104 and being unawareof roamer's registration with second VPMN 108, ITR module 130 sends afake LUP message to HLR-H 110, which will then send a CancelLocationmessage to second VPMN 108. As second VPMN 108 will not send any networkfailure to roamer 106's handset, roamer 106's handset is unaware ofCancelLocation and may get stuck for receiving any calls and SMS. Itwill be apparent to a person skilled in the art, that the MO activitiesof roamer 106 will not be affected due to any of the two stuck handsetcases, and hence roamer 106 will still be able to initiate MO calls andSMS. Therefore, a mechanism is required to handle the two cases ofhandset stuck in order to allow MT calls and SMS for the roamer. Thismechanism is based on sending the routing request, such as SRI, SRI-SMand ATI, prior to sending the fake LUP message from ITR module 130 toHLR-H 110.

FIGS. 7A, 7B, and 7C represent a flow diagram for handling a stuckhandset case, when the roamer's handset is stuck during its registrationattempt at the competitor network, in accordance with a first embodimentof the present invention. Roamer 106 attempts to (or is forced toattempt to) register with second VPMN 108 due to one or more reasons asdescribed above. At step 702, VLR-V2 114 sends an LUP message to HLR-H110. At step 704, HLR-H 110 sends the one or more registrationcancellation messages, such as CancelLocation message to VLR-V1 112, toabort roamer 106's registration with first VPMN 104. Detection unit 132detects the receipt of the CancelLocation message at first VPMN 104. Atstep 706, HLR-H 110 sends another CancelLocation message. However, thistime ITR module 130 taps the CancelLocation message.

Thereafter, at step 708, ITR module 130 sends an SRI-SM message to HLR-H110, to retrieve a VMSC/VLR address of roamer 106. At step 710, ITRmodule 130 attempts to redirect the traffic to first VPMN 104 by sendingthe fake LUP messages to HLR-H 110. In an embodiment of the presentinvention, ITR module 130 sends the fake LUP message to HLR-H 110,without waiting for an SRI-SM ACK message from HLR-H 110. At step 712,HLR-H 110 returns the SRI-SM ACK message to ITR module 130 that providesa VMSC/VLR address of second VPMN 108 to ITR module 130. The VMSC/VLRaddress is provided because of the previous LUP message from second VPMN108 that updated HLR-H 110 with its VMSC/VLR address.

For each registration cancellation message detected, ITR module 130sends the one or more fake LUP messages within a first pre-definedinterval of time (T0) until one registration message is recorded as asuccessful transaction. At step 714, HPMN 102 successfully completes theregistration process of roamer 106 with first VPMN 104, which causesHLR-H 110 to send a CancelLocation message to second VPMN 108, at step716. At step 718, VMSC/VLR-V2 114 in second VPMN 108 generates a networkfailure at roamer 106's handset, causing roamer 106's handset to bestuck for any further MT activities.

The mechanism that handles the stuck handset case, uses the VMSC/VLRaddress of second VPMN (i.e. VMSC/VLR-V2 114) i.e., retrieved at step712, to allow roamer 106 to receive MT calls and SMS on his handset,thereby facilitating roamer 106's mobile communication in second VPMN108. At step 720, ITR module 130 sends a new registration message, i.e.a new fake LUP using the VMSC/VLR-V2 address to HLR-H 110. This replacesa previous VMSC/VLR address stored at HLR-H 110 with the VMSC/VLR-V2address of roamer 106. Since, HLR-H 110 now has the actual VMSC/VLRaddress of roamer 106, MT calls on an MSISDN of roamer 106 are possible.In an embodiment of the present invention, when a GMSC associated withHPMN 102 receives a call request, intended for roamer 106's MSISDN, theGMSC sends a routing request message, such as SRI to HLR-H 110, whichissues a MAP PRN request to VMSC/VLR-V2 114. VMSC/VLR-V2 114 will returna Mobile Station Roaming Number (MSRN) corresponding to roamer 106'sMSISDN, to HLR-H 110. Second VPMN 108 and HPMN 102 will exchangesignaling messages like MAP RestoreData and MAP ISD to retrieve roamer106's profile information at VMSC/VLR-V2 114. Since, VMSC/VLR-V2 114 hasno information about the location area of roamer 106 and any radiocontact for establishing the ongoing call in second VPMN 108,VMSC/VLR-V2 114 uses a MAP SearchMS message to determine the exactlocation of roamer 106. Therefore, the MT call on roamer 106's MSISDN issuccessfully established using the present mechanism.

In an MT SMS case, when a ForwardSMS is received at VMSC/VLR-V2 114 andit has no record of roamer 106's current location in second VPMN 108; itwill not issue any MAP signaling messages, such as RestoreData andSearchMS, as done in the case of MT call on roamer 106's MSISDN. Thus,the SMS will not be delivered to roamer 106's handset. Even though theroamer is unable to receive the MT SMS, he can still receive the SMSlater, i.e., when his handset is not stuck. This is because the SMSdelivery uses store and forward technique, where the SMSC of theroamer's home network stores this SMS and delivers the SMS when theroamer registers back with a network (like first VPMN or second VPMN).

In an alternate embodiment of the present invention, ITR module 130 caninitiate a call setup request, towards roamer 106's MSISDN to causerestoration of roamer 106's profile information at VMSC/VLR-V2 114.Hence, at step 722, ITR module 130 initiates the call setup request,such as ISUP IAM, towards HLR-H 110, using a fake number (‘X’) as acalling party address (CgPA) and roamer 106's MSISDN as the called partyaddress (CdPA). In an embodiment of the present invention, this fakecall setup request is sent immediately after sending the new fake LUPmessage (i.e. at step 720) from ITR module 130 to HLR-H 110. At step724, HLR-H 110 sends a PRN request to VMSC/VLR-V2 114, which returns aPRN-ACK message to HLR-H 110, at step 726. Thereafter, at step 728,VMSC/VLR-V2 114 sends a RestoreData message to HLR-H 110, which sends anISD message back to VMSC/VLR-V2 114, at step 730, in order to updateVMSC/VLR-V2 114 with roamer 106's profile information. VMSC/VLR-V2 114returns an acknowledgement message, such as ISD-ACK, to HLR-H 110 atstep 732.

Further, at step 734, HLR-H 110 returns an acknowledgement message, suchas RestoreData-ACK message, to VMSC/VLR-V2 114 (in response to theRestoreData message, i.e., at step 728). At step 736, HLR-H 110 sends anISUP Address Completion Message (ACM) to ITR module 130, to confirm thatthe trunks are reserved for the call setup. Finally, at step 738, ITRmodule 130 releases the ongoing call by sending a release message, suchas an ISUP REL, to HLR-H 110. In an embodiment of the present invention,in case ITR module 130 does not detect any ISUP REL message, it sendsthe ISUP REL message to HLR-H 110, immediately after receiving the ISUPACM message. In another embodiment of the present invention, in order toavoid jamming the switch circuits or incurring charges, ITR module 130'sfake ISUP IAM message can be immediately followed by an ISUP RELmessage, after a pre-defined configurable time interval has passed. Thistime interval is configurable by the operator in first VPMN 104.

In another embodiment of the present invention, ITR module 130 can senda roaming number query to HLR-H 110, to cause restoration of roamer106's profile information at VMSC/VLR-V2 114. In this solution, ITRmodule 130 sends a MAP PRN on the VMSC/VLR-V2 114 (i.e. retrieved atstep 712) with a Signal Connection Control part (SCCP) Called Partyaddress (CdPA) Sub System Number (SSN) set to 7 (i.e. VLR type).However, this solution is possible only if the two competitor networks(i.e. first VPMN and second VPMN) allow direct SS7 interactions, and theVMSC/VLR-V2 114 does not check whether the PRN requesting party has aroaming relationship with its VPMN (i.e. second VPMN 108). Then,VMSC/VLR-V2 114 issues RestoreData message to HLR-H 110, to gain roamer106's profile information, when the roamer 106's handset is stuck insecond VPMN 108. This solution will avoid the requirement of tying upthe voice trunks and possibly incurring charges due to early callforwarding or late call forwarding.

Another alternative is for ITR module 130 to send a routing informationquery to HLR-H 110, to cause restoration of roamer 106's profileinformation at VMSC/VLR-V2 114. In this solution, ITR module 130 sends aMAP SRI message on roamer 106's MSISDN, to HPMN 102. Again, VMSC/VLR-V2114 will issue a RestoreData message to HLR-H 110, in order to gainstuck roamer 106's profile information. It will be apparent to a personskilled in the art that, many networks block SRI query from anothernetwork. This alternate solution will be applicable in cases where thenetwork does not block the SRI query from another network. In yetanother embodiment of the present invention, the fake ISUP messageapproach can be applied to a stuck roamer of a network optionally basedon percentage distribution as per the operator's configuration. Forexample, a maximum of five fake ISUP messages in an hour for a network Xor only 5% of stuck handsets of network X will be issued fake ISUPmessages.

FIGS. 8A, 8B, and 8C represent a flow diagram for handling a stuckhandset case, when the roamer's handset is stuck after it successfullyregisters with the competitor VPMN network, in accordance with a secondembodiment of the present invention. In this embodiment the roamer'shandset is unaware of the CancelLocation message received at second VPMN108 from HPMN 102, as roamer has successfully completed its registrationprocess with second VPMN 108, prior to receiving this CancelLocationmessage. At step 802, second VPMN 108 successfully completes theregistration process with HPMN 102. Steps 804 to 816 are similar tosteps 704 to 716, in which first VPMN 104 receives a CancelLocationmessage to abort the roamer 106's registration with first VPMN 104.However, in this embodiment, ITR module 130 is not aware that roamer 106is already registered with second VPMN 108. Upon receiving aCancelLocation message from HPMN 102, ITR module 130 sends an SRI toretrieve a VMSC/VLR address in second VPMN 108, followed by the fake LUPmessages to HLR-H 110 to complete the registration process with firstVPMN 104. This causes, HLR-H 110 to send a CancelLocation message tosecond VPMN 108, at step 816.

Now, since roamer 106 is already registered with second VPMN 108,VMSC/VLR-V2 114 neither responds to the CancelLocation message fromHLR-H 110, nor does it send any failure message, such as network failureat roamer 106's handset. In other words, roamer 106's handset is unawarethat it got stuck. Therefore, roamer 106's handset is unable to performany MT activities, such as MT calls and MT SMS. Rest of the steps 818 to836 are also similar to steps 720 to 738, where ITR module 130 sends anew fake LUP message to HLR-H 110, using the VMSC/VLR-V2 address toupdate HLR-H 110 with the real VMSC/VLR address. Further, ITR module 130may initiate a fake call setup to allow MT calls on roamer 106's MSISDN.In addition, various embodiments for the MT SMS and the MT call on theroamer's MSISDN as explained in FIGS. 7A, 7B, and 7C are also applicablefor FIGS. 8A, 8B, and 8C.

The present invention can take the form of an entirely hardwareembodiment, an entirely software embodiment, or an embodiment containingboth hardware and software elements. In accordance with an embodiment ofthe present invention, software, including but not limited to, firmware,resident software, and microcode, implements the invention.

Furthermore, the invention can take the form of a computer programproduct, accessible from a computer-usable or computer-readable mediumproviding program code for use by, or in connection with, a computer orany instruction execution system. For the purposes of this description,a computer-usable or computer readable medium can be any apparatus thatcan contain, store, communicate, propagate, or transport the program foruse by or in connection with the instruction execution system,apparatus, or device.

The medium can be an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system (or apparatus or device) or apropagation medium. Examples of a computer-readable medium include asemiconductor or solid state memory, magnetic tape, a removable computerdiskette, a random access memory (RAM), a read-only memory (ROM), arigid magnetic disk and an optical disk. Current examples of opticaldisks include compact disk-read only memory (CDROM), compactdisk-read/write (CD-R/W) and Digital Versatile Disk (DVD).

A computer usable medium provided herein includes a computer usableprogram code, which when executed, redirects roaming traffic of a roamerassociated with an HPMN. The computer program product further includes acomputer usable program code for detecting by a detection unit coupledto a first VPMN, a registration attempt of the roamer at a second VPMN,upon receipt of a first registration cancellation message of one or moreregistration cancellation messages that is sent by the HPMN. Thecomputer program product further includes a computer usable program codefor sending one or more registration messages to the HPMN from aredirection unit coupled to the first VPMN to cause the HPMN to send aregistration response message to a VLR associated with the second VPMN,to thwart the registration attempt of the roamer at the second VPMN. Theredirection unit further facilitates the roamer's mobile communicationwhen the roamer's handset gets stuck in the second VPMN.

A VPMN operator uses one or more variations of the present invention toallow him to perform traffic redirection on the inbound roamers of HPMN,in order to cause a competitor VLR abort to the inbound roamer'sregistration attempt at a competitor VPMN. The present invention helpsthe VPMN operators to retain these inbound roamers on their respectivenetworks. The present invention further allows VPMN operators to handlevarious cases when the inbound roamer's handset is stuck, either duringits registration attempt with the competitor VPMN or after itssuccessful registration with the competitor VPMN. This handling of stuckhandset cases, allows the stuck inbound roamers to perform various MOand MT call and non-call related activities in the competitor VPMNs. TheVPMN operator may also be able to authenticate the inbound roamers ifHPMN requires so. The present invention allows the VPMN operator tocreate a fake distribution image of its competitor VPMN at an HPMN HLRthat eventually results in maximizing roaming revenues for the VPMNoperator.

The components of present system described above include any combinationof computing components and devices operating together. The componentsof the present system can also be components or subsystems within alarger computer system or network. The present system components canalso be coupled with any number of other components (not shown), such asother buses, controllers, memory devices, and data input/output devices,in any number of combinations. In addition, any number or combination ofother processor-based components may be carrying out the functions ofthe present system.

It should be noted that the various components disclosed herein may bedescribed using computer aided design tools and/or expressed (orrepresented), as data and/or instructions embodied in variouscomputer-readable media, in terms of their behavioral, registertransfer, logic component, transistor, layout geometries, and/or othercharacteristics. Computer-readable media in which such formatted dataand/or instructions may be embodied include, but are not limited to,non-volatile storage media in various forms (e.g., optical, magnetic orsemiconductor storage media) and carrier waves that may be used totransfer such formatted data and/or instructions through wireless,optical, or wired signaling media or any combination thereof.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense as opposed to anexclusive or exhaustive sense; that is to say, in a sense of “including,but may not be limited to.” Words using the singular or plural numberalso include the plural or singular number respectively. Additionally,the words “herein,” “hereunder,” “above,” “below,” and words of similarimport refer to this application as a whole and not to any particularportions of this application. When the word “or” is used in reference toa list of two or more items, it covers all of the followinginterpretations: any of the items in the list, all of the items in thelist and any combination of the items in the list.

The above description of illustrated embodiments of the present systemis not intended to be exhaustive or to limit the present system to theprecise form disclosed. While specific embodiments of, and examples for,the present system are described herein for illustrative purposes,various equivalent modifications are possible within the scope of thepresent system, as those skilled in the art will recognize. Theteachings of the present system provided herein can be applied to otherprocessing systems and methods. They may not be limited to the systemsand methods described above.

The elements and acts of the various embodiments described above can becombined to provide further embodiments. These and other changes can bemade in light of the above detailed description.

Other Variations

Provided above for the edification of those of ordinary skill in theart, and not as a limitation on the scope of the invention, are detailedillustrations of a scheme for redirecting roaming traffic of a roamerassociated with an HPMN. Numerous variations and modifications withinthe spirit of the present invention will of course occur to those ofordinary skill in the art in view of the embodiments that have beendisclosed. For example, the present invention is implemented primarilyfrom the point of view of GSM mobile networks as described in theembodiments. However, the present invention may also be effectivelyimplemented on GPRS, 3G, CDMA, WCDMA, WiMax etc., or any other networkof common carrier telecommunications in which end users are normallyconfigured to operate within a “home” network to which they normallysubscribe, but have the capability of also operating on otherneighboring networks, which may even be across international borders.

The examples under the system of present invention detailed in theillustrative examples contained herein are described using terms andconstructs drawn largely from GSM mobile telephony infrastructure.However, use of these examples should not be interpreted as limiting theinvention to those media. The system and method can be of use andprovided through any type of telecommunications medium, includingwithout limitation: (i) any mobile telephony network including withoutlimitation GSM, 3GSM, 3G, CDMA, WCDMA or GPRS, satellite phones or othermobile telephone networks or systems; (ii) any so-called WiFi apparatusnormally used in a home or subscribed network, but also configured foruse on a visited or non-home or non-accustomed network, includingapparatus not dedicated to telecommunications such as personalcomputers, Palm-type or Windows Mobile devices; (iii) an entertainmentconsole platform such as Sony Playstation, PSP or other apparatus thatare capable of sending and receiving telecommunications over home ornon-home networks, or even (iv) fixed-line devices made for receivingcommunications, but capable of deployment in numerous locations whilepreserving a persistent subscriber id such as the eye2eye devices fromDlink; or telecommunications equipment meant for voice over IPcommunications such as those provided by Vonage or Packet8.

In describing certain embodiments of the system under the presentinvention, this specification follows the path of a telecommunicationscall, from a calling party to a called party. For the avoidance ofdoubt, such a call can be a normal voice call, in which the subscribertelecommunications equipment is also capable of visual, audiovisual ormotion-picture display. Alternatively, those devices or calls can be fortext, video, pictures or other communicated data.

In the foregoing specification, specific embodiments of the presentinvention have been described. However, one of ordinary skill in the artwill appreciate that various modifications and changes can be madewithout departing from the scope of the present invention as set forthin the claims below. Accordingly, the specification and the figures areto be regarded in an illustrative rather than a restrictive sense, andall such modifications are intended to be included within the scope ofpresent invention. The benefits, advantages, solutions to problems, andany element(s) that may cause any benefit, advantage, or solution tooccur, or to become more pronounced, are not to be construed as acritical, required, or essential feature or element of any or all of theclaims.

APPENDIX Acronym Description 3G Third Generation of mobile 3GPP ThirdGeneration Partnership Project ACM ISUP Address Completion Message ANMISUP Answer Message ATI Any Time Interrogation BCSM Basic Call StateModel BSC Base Station Controller CDMA Code Division Multiplexed AccessCdPA Called Party Address CgPA Calling Party Address DPC DestinationPoint Code DSD Delete Subscriber Data ERB CAP Event Report Basic callstate model GLR Gateway Location Register GMSC Gateway MSC GSM GlobalSystem for Mobile GT Global Title HLR Home Location Register HLR-FForward-to number HLR HLR-H HPMN HLR HLR-V VPMN HLR HPMN Home PublicMobile Network GTT Global Title Translation IAM Initial Address MessageIMSI International Mobile Subscriber Identity IMSI-H HPMN IMSI ISCInternational Service Carrier ISD MAP Insert Subscriber Data ISTPInternational STP ISUP ISDN User Part ITR Inbound Traffic Redirection LULocation Update LUP MAP Location Update MAP Mobile Application Part MOMobile Originated MSC Mobile Switching Center MSISDN Mobile StationInternational Subscriber Directory Number MSISDN-H HPMN MSISDN MSRNMobile Station Roaming Number MT Mobile Terminated MTP Message TransferPart NP Numbering Plan NPI Numbering Plan Indicator OCN OriginallyCalled Number ODB Operator Determined Barring OTA Over The Air PRN MAPProvide Roaming Number PSL Provide Subscriber Location PSI MAP ProvideSubscriber Information REL ISUP Release Message RI Routing Indicator RNARoaming Not Allowed RR Roaming Restricted RRB CAP Request Report Basiccall state model RSD ReStore Data SAI Send Authentication InformationSCCP Signal Connection Control part SCP Signaling Control Point SGSignaling Gateway SIM Subscriber Identity Module SMS Short MessageService SMSC Short Message Service Center SPC Signal Point Code SRI MAPSend Routing Information SRI-LCS MAP Send Routing Information ForLoCation Service SRI-SM MAP Send Routing Information For Short MessageSS7 Signaling System #7 SSN Sub System Number SSP Service Switch PointSTP Signal Transfer Point TCAP Transaction Capabilities Application PartTR Traffic Redirection TT Translation Type VAS Value Added Service VLRVisited Location Register VLR-V VPMN VLR VMSC Visited Mobile SwitchingCenter VMSC-V VPMN VMSC VPMN Visited Public Mobile Network

TECHNICAL REFERENCES (EACH OF WHICH IS INCORPORATED BY THIS REFERENCEHEREIN)

-   “Method And System For Cellular Network Traffic redirection”    application Ser. No. 10/635,804 filed on Aug. 5, 2003.-   “Method and Apparatus for Defense Against Network Traffic    redirection” Application No. 60/662,030 filed Mar. 14, 2005.-   Q71X SCCP-   Q70X MTP-   Q77X TCAP-   GSM 1111 SIM and Mobile Interface-   GSM 1114 SIM Toolkit-   IR 7320 Steering of Roaming-   GSM 902 on MAP specification-   Digital cellular telecommunications system (Phase 2+)-   Mobile Application Part (MAP) Specification-   (3GPP TS 09.02 version 7.9.0 Release 1998)-   GSM 340 on SMS-   Digital cellular telecommunications system (Phase 2+);-   Technical realization of the Short Message Service (SMS);-   (GSM 03.40 version 7.4.0 Release 1998)-   GSM 348 Security and OTA,-   GSM 31048 Security and OTA,-   GSM 23119 Gateway Location Register,-   GSM 408 Mobile Radio Interface Network Layer-   GSM 23122 Mobile Station Procedure-   GSM 24008 Mobile Radio Interface Network Layer-   GSM22011 Service Accessibility-   GSM25304 Idle Mode Selection-   GSM29010 Error Network Mapping-   GSM 29002 MAP Protocol

1. A method for redirecting roaming traffic of a roamer having a handset, the roamer being associated with a Home Public Mobile Network (HPMN) and initially registered with a first Visited Public Mobile Network (VPMN), the first VPMN coupled to a redirection unit, the method comprising: detecting, at the first VPMN, a registration attempt of the roamer at a second VPMN, upon receipt of a first of one or more registration cancellation messages sent by the HPMN; sending one or more registration messages from the redirection unit to the HPMN; and causing, based on the one or more registration messages, the HPMN to send a registration response message to a Visited Location Register (VLR) associated with the second VPMN to thwart the registration attempt of the roamer at the second VPMN; wherein the redirection unit facilitates the roamer's mobile communication when the roamer's handset is stuck in the second VPMN.
 2. The method of claim 1, the HPMN having an associated Home Location Register (HLR), the method further comprising: authenticating the roamer with the HPMN by sending one or more authentication messages, prior to sending the one or more registration messages, from the redirection unit to the HLR.
 3. The method of claim 1, the HPMN having an associated Home Location Register (HLR), the method further comprising: in response to the registration response message, sending the one or more registration messages successively to the HPMN, thereby causing the VLR to send an abort message to the HLR.
 4. The method of claim 3 further comprising: blacklisting the HLR and the VLR to restrict the redirection unit from sending further registration messages to the HPMN within a pre-defined time interval, upon the occurrence of one selected from a group consisting of the VLR failing to send the abort message to the HLR, and the HLR failing to send the registration response message to the VLR.
 5. The method of claim 1, the HPMN having an associated Home Location Register (HLR), the method further comprising: blacklisting the HPMN when the HLR fails to return a Visited Mobile Switching Center (VMSC) address in response to a routing information query from the redirection unit to the HLR, wherein the blacklisting is performed to restrict the redirection unit from sending a further routing information query to the HLR.
 6. The method of claim 1, the HPMN having an associated Home Location Register (HLR) and the redirection unit having an address, the method further comprising: sending another one of the one or more registration messages using a VMSC address and a VLR address associated with the second VPMN, from the redirection unit to the HLR, for updating the address of the redirection unit with the VMSC address and the VLR address.
 7. The method of claim 6, the roamer having a profile information at the VLR and an associated Mobile Station International Subscriber Directory Number (MSISDN), the method further comprising: initiating a call setup request from the redirection unit to the MSISDN number of the roamer for restoring the roamer's profile information at the VLR, thus facilitating the roamer's mobile communication.
 8. The method of claim 6, the roamer having a profile information at the VLR, the method further comprising: sending a routing information query from the redirection unit to the HLR for restoring the roamer's profile information at the VLR, thus facilitating the roamer's mobile communication.
 9. The method of claim 6, the roamer having a profile information at the VLR, the method further comprising: sending a roaming number query from the redirection unit to the VLR for restoring the roamer's profile information at the VLR, thus facilitating the roamer's mobile communication.
 10. The method of claim 1, the HPMN having an associated Home Location Register (HLR) and the redirection unit having an address at the HLR, the method further comprising: upon receipt of the address of the redirection unit in response to a routing information query sent from the redirection unit to the HLR, sending a registration location detached message to the HLR to remove the address of the redirection unit from the HLR, when thwarting the registration attempt of the roamer at the second VPMN fails.
 11. A system for redirecting roaming traffic of a roamer having a handset, the roamer being associated with a Home Public Mobile Network (HPMN) and initially registered with a first Visited Public Mobile Network (VPMN), the system comprising: a detection unit coupled to a first VPMN for detecting a registration attempt of the roamer at a second VPMN, upon receipt of a first of one or more registration cancellation messages sent by the HPMN; and a redirection unit coupled to the first VPMN for sending one or more registration messages to the HPMN to cause the HPMN to send a registration response message to a Visited Location Register (VLR) associated with the second VPMN for thwarting the registration attempt of the roamer at the second VPMN; wherein the redirection unit facilitates the roamer's mobile communication when the roamer's handset is stuck in the second VPMN.
 12. The system of claim 11, the HPMN having an associated Home Location Register (HLR), the system further comprising: at the redirection unit, means for sending the one or more registration messages successively to the HPMN for causing the VLR to send an abort message to the HLR in response to the registration response message.
 13. The system of claim 12, further comprising: means for blacklisting the HLR and the VLR to restrict the redirection unit from sending further registration messages to the HPMN within a pre-defined time interval, upon the occurrence of one selected from a group consisting of the VLR failing to send the abort message to the HLR, and the HLR failing to send the registration response message to the VLR.
 14. The system of claim 11, the HPMN having an associated Home Location Register (HLR), the system further comprising: means for blacklisting the HPMN when the HLR fails to return a Visited Mobile Switching Center (VMSC) address in response to a routing information query from the redirection unit to the HLR, wherein the blacklisting is performed to restrict the redirection unit from sending a further routing information query to the HLR.
 15. The system of claim 11, the HPMN having an associated Home Location Register (HLR) and the redirection unit having an address, the system further comprising: means for sending another one of the one or more registration messages using a VMSC address and a VLR address associated with the second VPMN, from the redirection unit to the HLR, for updating the address of the redirection unit with the VMSC address and the VLR address.
 16. The system of claim 11, the HPMN having an associated Home Location Register (HLR) and the redirection unit having an address at the HLR, the system further comprising: means for sending a registration location detached message to the HLR to remove the address of the redirection unit from the HLR, upon receipt of the address of the redirection unit in response to a routing information query sent from the redirection unit to the HLR, when thwarting the registration attempt of the roamer at the second VPMN fails.
 17. A computer program product comprising a computer usable non-transitory medium having a computer usable program code stored thereon for redirecting roaming traffic of a roamer having a handset, the roamer being associated with a Home Public Mobile Network (HPMN) and initially registered with a first Visited Public Mobile Network (VPMN), the first VPMN coupled to a redirection unit, the computer program product comprising: first computer usable program code means for detecting, at the first VPMN, a registration attempt of the roamer at a second VPMN, upon receipt of a first of one or more registration cancellation messages sent by the HPMN; second computer usable program code means for sending one or more registration messages from the redirection unit to the HPMN; and third computer usable program code means for causing, based on the one or more registration messages, the HPMN to send a registration response message to a Visited Location Register (VLR) associated with the second VPMN to thwart the registration attempt of the roamer at the second VPMN; wherein the redirection unit facilitates the roamer's mobile communication when the roamer's handset is stuck in the second VPMN.
 18. The computer program product of claim 17, the HPMN having an associated Home Location Register (HLR), the computer program product further comprising: fourth computer usable program code means for authenticating the roamer with the HPMN by sending one or more authentication messages, prior to sending the one or more registration messages, from the redirection unit to the HLR.
 19. The computer program product of claim 17, the HPMN having an associated Home Location Register (HLR), the computer program product further comprising: fifth computer usable program code means for sending, in response to the registration response message, the one or more registration messages successively to the HPMN, thereby causing the VLR to send an abort message to the HLR.
 20. The computer program product of claim 19 further comprising: fifth computer usable program code means for blacklisting the HLR and the VLR to restrict the redirection unit from sending further registration messages to the HPMN within a pre-defined time interval, upon the occurrence of one selected from a group consisting of the VLR failing to send the abort message to the HLR, and the HLR failing to send the registration response message to the VLR. 